The invention relates to munitions and firearms.
This invention has particular, but not exclusive, application to a barrel having a plurality of projectiles stacked axially within the barrel together with discrete selectively ignitable propellant charges for propelling the projectiles sequentially through the muzzle of the barrel. Such barrels will be referred to hereinafter as of the type described.
International Patent Application No. PCT/AU94/00124 relates to firearms of the type described. Field tests of prototype versions of firearms utilizing barrels of the type described have shown that such barrel assemblies perform to expectations. However the inventor has proposed useful variations, including munitions, as well as improvements which may assist in either the efficient production of such firearms or facilitate their performance or useability. Furthermore the inventor envisages that single barrel rates of fire in excess of 40,000 rounds/minute may be achievable in practice and this possibility creates further scope for munitions of conventional style and firearms utilizing barrels of the-type described.
According to one aspect this invention provides a barrel assembly of the type described, wherein:
adjacent projectiles are separated from one another and maintained in spaced apart relationship by locating means separate from the projectiles, and
each projectile includes expandable sealing means for forming an operative seal with the bore of the barrel.
The locating means may be the propellant charge between adjacent projectiles and the sealing means suitably includes a skirt portion of each projectile which expands outwardly when subject to an in-barrel load. The in-barrel load may be applied during installation of the projectiles or after loading such as by tamping to consolidate the column of projectiles and propellant charges or it may result from the firing of an outer projectile and particularly the adjacent outer projectile.
The propellant charge may be form as a solid block to operatively space the projectiles in the barrel or the propellant charge may be encased in metal or other rigid case which may include an embedded primer having external contact means adapted for contacting an pre-positioned electrical contact associated with the barrel. For example the primer could be provided with a sprung contact which may be retracted to enable insertion of the cased charge into the barrel and to spring out into a barrel aperture upon alignment with that aperture for operative contact with its mating barrel contact. If desired the outer case may be consumable or may chemically assist the propellant burn. Furthermore an assembly of stacked and bonded or separate cased charges and projectiles may be provide for reloading a barrel.
The rear end of the projectile may be formed with a skirt about an inwardly reducing recess such as a conical recess or a part-spherical recess or the like into which the propellant charge portion extends and about which rearward movement of the projectile will result in radial expansion of the projectile skirt. This rearward movement may occur by way of compression resulting from a rearward wedging movement of the projectile along the leading portion of the propellant charge it may occur as a result of metal flow from the relatively massive leading part of the projectile to its less massive skirt portion.
Alternatively the projectile may be provided with a rearwardly divergent peripheral sealing flange or collar which is deflected outwardly into sealing engagement with the bore upon rearward movement of the projectile. Furthermore the sealing may be effected by inserting the projectiles into a heated barrel which shrinks onto respective sealing portions of the projectiles. Then again the projectile may comprise a relatively hard mandrel portion located by the propellant charge and which cooperates with a deformable annular portion supported thereabout for expansion into operative sealing engagement with the bore. The deformable annular portion may be moulded about the mandrel to form a unitary projectile which relies on metal flow between the nose of the projectile and its tail for outward expansion about the mandrel portion into sealing engagement with the bore of the barrel.
In a further embodiment the projectile assembly includes a rearwardly expanding anvil surface supporting a sealing collar thereabout and adapted to be radially expanded into sealing engagement with the barrel bore upon forward movement of the projectile through the barrel. In such embodiment it is preferred that the propellant charge have a cylindrical leading portion which abuts the flat end face of the projectile.
If desired, the projectiles may be adapted for seating and/or location within circumferential grooves or by annular ribs in the bore or in rifling grooves in the bore and may include a metal jacket encasing at least the outer end portion of the projectile. The projectile may be provided with contractible peripheral locating rings which extend outwardly into annular grooves in the barrel and which retract into the projectile upon firing to permit its free passage through the barrel.
In another aspect this invention resides broadly in a method of electrical ignition for sequentially igniting the propellant charges of a barrel assembly of the type described, including:
igniting the leading propellant charge by sending an ignition signal through the stacked projectiles, and
causing ignition of the leading propellant charge to arm the next propellant charge for actuation by the next ignition signal. Suitably all propellant charges inwardly from the end of a loaded barrel are disarmed by the insertion of respective insulating fuses disposed between normally closed electrical contacts.
Ignition of the propellant may be achieved electrically or ignition may utilise conventional firing pin type methods such as by using a centre-fire primer igniting the outermost projectile and controlled consequent ignition causing sequential ignition of the propellant charges of subsequent rounds. This may be achieved by controlled rearward leakage of combustion gases or controlled burning of fuse columns extending through the projectiles.
In another form the ignition is electronically controlled with respective propellant charges being associated with primers which are triggered by distinctive ignition signals. For example the primers in the stacked propellant charges may be sequenced for increasing pulse width ignition requirements whereby electronic controls may selectively send ignition pulses of increasing pulse widths to ignite the propellant charges sequentially in a selected time order. Preferably however the propellant charges are ignited by a set pulse width signal and burning of the leading propellant charge arms the next propellant charge for actuation by the next emitted pulse.
Suitably in such embodiments all propellant charges inwardly from the end of a loaded barrel are disarmed by the insertion of respective insulating fuses disposed between normally closed electrical contacts, the fuses being set to burn to enable the contacts to close upon transmission of a suitable triggering signal and each insulating fuse being open to a respective leading propellant charge for ignition thereby.
A number of projectiles can be fired simultaneously, or in quick succession, or in response to repetitive manual actuation of a trigger, for example. In such arrangements the electrical signal may be carried externally of the barrel or it may be carried through the superimposed projectiles which may clip onto one another to continue the electrical circuit through the barrel, or abut in electrical contact with one another. The projectiles may carry the control circuit or they may form a circuit with the barrel.
An advantage which is likely to be gained from dispensing with externally fired primers is the removal of lateral forces within the barrel from firing of the wall mounted primers and the resultant uneven deposit from the primer firing on the projectile and/or barrel. This may increase the accuracy of such weapons and simplify refurbishing of used barrels.
In a further aspect this invention resides broadly in a cased round including:
a case adapted for retention in a breech assembly;
at least two projectiles disposed one behind the other in the case and each being sealably engaged therewith;
respective propellant charges within the case and behind each projectile, and
ignition means for igniting the charges in a predetermined sequence. The ignition means may be an electrical ignition means of the type described above or in the abovementioned earlier International Patent Application, but preferably the ignition means utilises mechanical operation of pin fired primers.
The pin fired primer may be adapted to ignite the outermost propellant charge which burns back to ignite the rear charge, but preferably the case is provided with respective primers associated with separate pins for firing the primers. Suitably the primers includes a centre-fire primer associated with a rearwardly extending tubular central spine of the rearmost projectile assembly providing a gas path or burn path for conveying the primer burn to the forward propellant and a rim-fire primer for igniting the rear propellant charge. Alternatively the hollow rear spine may be independent of the rear projectile and support an extension pin conveying the mechanical pin action to a primer supported at within or forwardly of the rear projectile and communicating with the forward propellant.
If desired the centre-fire primer may be associated with the rear propellant charge and the rim fire primer may be disposed in the casing wall in direct communication with the outermost or an outer charge.
The mechanical impacts with the primers may be in quick succession so as to enable both projectiles to be fired sequentially at a rapid rate, such as at a rate of greater than 40,000 rounds per minute. For this purpose where both primers are associated with the base of the cartridge the firing pins may be formed integrally, with the outer pin being slightly shorter than the central pin for the required actuating delay. Suitably the cased ammunition is adapted for use with a rifle or hand gun which includes a preset time delay for, or be provided with a selectively variable timing differential between, actuation of the firing pins.
The timing of the firing of a pair of adjacent projectiles in the above cased ammunition embodiment or in the barrel assembly may be such as to delay ignition of the forward propellant until after the adjacent projectiles have moved as an assembly part-way down the barrel in response to ignition of the rear propellant. This arrangement is proposed as a means of increasing the velocity of the forward projectile. That is the kinetic energy of the rear projectile of a pair of projectiles is sacrificed to enhance the kinetic energy of the front projectile. Alternatively the firing of the rear propellant may follow the firing of the forward propellant simultaneously or almost immediately while the leading projectile remains in the barrel to impart its effect, at least in part, to the forward projectile.
Another variation of the present invention which may be applied to the barrel version or the cased ammunition version of the invention aims to deflect the projectile from its axial path on exiting the barrel by providing a gas bypass passage adjacent the muzzle which feeds propellant gases back to the barrel in the path of the projectile so as to deflect its trajectory from the end of the barrel. In a preferred form such modified barrels are arranged as a cluster of barrels with the bypass bleed inlets innermost so that the lateral reaction forces produced cancel one another.
Furthermore ammunition utilizing a rearwardly extending spine may be provided with flight stabilizers such as fins which may be utilized to cause rotation of the projectile to cause rotation in a projectile fired from a smooth bore barrel, or to provide a non-rotating flight projectile. Additionally, projectiles may utilize a spine which projects forwardly from the nose of the projectile to provide the separation for propellant. Where means are used to induce rotation of the projectile such as barrel rifling, it may be advantageous to form the two part projectiles with opposite hand coarse or fine joining threads so that the rotation caused by the rifling tends to bind the parts together and not separate them as may be the case where the two part junction does not inhibit independent axial rotation of the projectile parts.